Field coil
（重定向自Bipolar field）
![Modern low-cost universal motor, from a vacuum cleaner. Field windings are dark copper colored, toward the back, on both sides. The rotor's laminated core is gray metallic, with dark slots for winding the coils. The commutator (partly hidden) has become dark from use; it's toward the front. The large brown molded-plastic piece in the foreground supports the brush guides and brushes (both sides), as well as the front motor bearing.](/Images/godic/202412/24/Universalmotor_31655.JPG")
![Salient field bipolar generator](/Images/godic/202412/24/Salient_pole_bipolar_series_field_generator21655.JPG")
![Consequent field bipolar generator](/Images/godic/202412/24/Consequent_pole_bipolar_series_field_DC_generator1655.jpg")
![Consequent field, four-pole, shunt-wound DC generator](/Images/godic/202412/24/Modern_Consequent-Pole_Four-Field_Shunt-Wound_DC_Generator1655.jpg")
A field coil is an electromagnet used to generate a magnetic field in an electro-magnetic machine, typically a rotating electrical machine such as a motor or generator. It consists of a coil of wire through which a current flows.
In a rotating machine, the field coils are wound on an iron magnetic core which guides the magnetic field lines. The magnetic core is in two parts; a stator which is stationary, and a rotor, which rotates within it. The magnetic field lines pass in a continuous loop or magnetic circuit from the stator through the rotor and back through the stator again. The field coils may be on the stator or on the rotor.